X-ray tube



Dec. 14, 1943. H. w.l BRACKNY ET AL 2,336,774

X-RAY TUBE Filed Aug. 18, 1941 "Rss-U i?atenied Dec. lli, i943 X-RAY TUBE Howard W. Brackney and Joseph B. Gosling, Chicago, lll., assignors to General Electric X-Ray Corporation, Chicago, Ill., a corporation of New York Application August 18, 1941, Serial No. 401,288

(Cl. :Z50-,155)

6 Claims.

The present invention relates in general to electronics and electron ow devices, having more particular reference to a multiple section X-ray generator having improved structural features for the control of electron flow.

An important object of the present invention is to provide for the prevention of the accumulation of electrical charges on the enclosing-envelope of an electron flow device, a further object being to prevent the deleterious effects produced by the building up of electrical charges as a result of electronic bombardment of the envelope walls in an electron iiow device.

Another important object is to provide for the successful operation of high tension electron flow devices in which, necessarily, the distance between the anode and cathode of the device is great, and wherein the device has substantial length as comparedwith its Width and wherein, consequently, there is appreciable tendency l :for wall charges to accumulate upon the envelope walls as a result of electron deviation in traveling an extended path between anode and cathode.

Another important object is to provide an electron ilow device of the character mentioned having an elongated sectional envelope and screening means for each section whereby to prevent electron impingement upon the sectional walls of the envelope;` a further object being to form the screening means as a series of electronic lenses whereby to maintain electrons emitted at the cathode at one end of the device in a predetermined path extending to the anode target at the opposite end of the envelope and thereby prevent electronic impingement upon the sectional envelope Walls; a'still further object being to provide a screen in the form of an electronic lens for each sectional envelope portion.

Another important object is to provide electronic immersion lenses for guiding electron flow in a device of the character mentioned; a further object being to form each lens as a screen having a portion extending within or immersed in a co-operating screen portion of an adjacent lens.

Another important object is to vprovide an electronic lens structure comprising. a series oi aligned screens supported at spaced intervals on the Walls of the device; a further object being to support the lenses on annular flanges on the envelope at spaced intervals; a further object being to utilize circularly spaced lugs on each lens for mounting it on its supporting flange; a

further object being to form the supporting flanges with spaced openings in angularly spaced position corresponding with the angular spacement of the lugs sothat atlens may be assembled on a desired support nange of a series by Dassing the lens successively through other support lugs of the series, the lugs of theA lens `passing through the slots of theY support iianges, and the lens being secured on. its support flange by fastening the lugs theretovin position oset .from the lug-passing slots.

Another important object is to provide a-sectional envelope comprising a series of cylindrical hollow glass .sections Asupported in' end-toend relationship, with the abutting ends of adjacent sections interconnected and secured to.- gether by metallic sealingcrings, .the opposite ends of which rings are each sealed, byra glass-v to-metaliseal, with the abutting end edges .ciadjacent glass envelope sections; aiurther object being to utilize the metallic seal rings for mounting electronic lenses rwithin the envelope; a further object,- to that end, being to provide the sealing rings With inwardly extending lens mountingflange means.

Another important object is to control .the electrical potential of each lens or shield,. as by electrically connecting the sealing vring Y,on which the lens is mounted with.,the transformer or other power vsource from which the `anode and cathode of the device are energized.

These and numerous other important objects, advantages, and inherent functions of theiinvention will become apparent las the invention is more fully understood from the followingdescription, which, taken in connection with the accompanying drawing, discloses preferredembodiments Vof the invention. l f

Referring tothe drawing:

Figure 1 is a sectionalview taken longitudinally through ahigh tension X-raygenerator;

Figure 2 is an enlarged sectional view of aportion of the device shown in Figure-1;

Figure 3 is an enlarged-sectional vie-w illustrating a modied arrangement of parts;

Figure 4 is an enlarged sectional view showing another modified arrangement;

Figure 5 is a sectional view `takensubstantially along the line 5 5 in Figures Sandri; and

Figure 6 is al sectional `view-taker-i substantially along the lineec in Figure 2'. Y

To illustrate the invention, the drawing shows an X-ra-y *generator li comprising an anodelt and a cathode l5 in opposed relationship enclosed within an envelope-Il of general-lytubular configuration, with the cathode at one end and the anode at the other.

The generator is adapted for operation with relatively high voltage values applied between the anode and cathode, which are relatively widely spaced, necessitating an elongated envelo-pe structure connning the electron flow path between the anode and cathode, the required envelope length being such as to render difficult the provision of an all glass envelope structure. The envelope, therefore, preferably comprises a series of cylindrical glass envelope sections I9 and glass end sections 22 and 24 arranged in end-to-end abutting relationship, the sections IS, 22 and 24 being interconnected by means of connecting rings 2i which are preferably` of metal and which have opposite ends forming glass-to-metal seals 23 with the facing ends of adjacent envelope sections I9, 22 and 24.

The envelope section 22 at the cathode end of the envelope has a re-entrant portionZ forming a gl'ass-to-metal seal 21 with a suitable skirt forming a part of the cathode structure.

At the anode end, the envelope comprises a target support tube 29 formed with a collar 3| which carries an annular sealing rim 33 sealed thereon, said rim 33 having an annular edge forming a glass-to-metal seal 35 with the glass envelope section 2t at the anode end of the envelope. The tube 29 has a closed end and an open end extending within said glass end section 24 and has an anode target 31 sealed within the closed end of the tube 29.

It should be understood, of course, that X-ray generators function to develop X-rays at the anode by impingement thereon of electrons emitted at the cathode, such electrons travelling from the cathode in an electron stream directed toward and impinging upon the anode target 3i,

the electrons being generated and liberated at the cathode as by electrically heating an electron emitting cathode element, and the electron stream being impelled toward the anode under the influence of electrical potential applied between' the anode and cathode as. from a suitable power source, usually the winding of an electrical transformer.

In passing from the cathode toward the anode, electrons may deviate from the desired path and impinge upon the walls of the envelope l1, such impingeinent building up electricalcharges on the surface of the envelope, which may become suiciently large to puncture the envelope, particularly at the seals 23 and 35. Electrical charges thus vbuilt up on the envelope as a result of elec- .fr

tron impingement thereon may also result in etching of the envelope, and such charges also may exert electrostatic effects upon the electron stream and disturb the even tenor of its flow.

In order to obviate the difficulties and disadvantages of the accumulation of charges on the envelope as a result of envelope bombardment by stray electrons, the present invention contemplates the provision of a series of electronic lenses or screens for maintaining electrons emitted at the cathode in a path toward the anode, thereby guiding the electrons in a desired Iiow path and preventing impingement thereof upon the envelope I1. To this end, a series of screens 39 cornprising electronic lenses are arranged in spaced relationship within the envelope between the anode and the cathode. These lenses or screens preferably comprise cylindrical metallic elements arranged in axial alignment and in spaced relationship between the anode and the cathode, the

elements being preferably disposed each opposite an envelope sealing ring 2i and supported thereon. As shown in Figure 4, the elements 353 may comprise hollow cylindrical shells having beaded edges di at the opposite ends of the elements, the facing ends of adjacent elements being spaced apart and the beaded edges serving to create electrostatic fields of force between adjacent elements for the purpose of retaining electrons against passage radially through the opening between adjacent elements.

Each element 39, however, as shown in Figures i, 2 and 3, preferably comprises sleeve-like means having one end larger than the other so that smaller end of one element may extend in iinmersed position within the larger end of the adjacent element, the opposite end edges being beaded as at 4I. While the elements 39 may be formed in any suitable or preferred fashion, they each may conveniently comprise a cylindrical shell 3 provided with the beaded edge 4i at one end and an inturned annular flange "l5 at the other end, thus constituting the shell as a cupshaped eleznent having a anged opening in its bottom. A tubular shell 41 of lesser diameter than the shell 43 is sealingly secured at one end in the opening defined by the fiange t5 in coaxial alignment with respect to the shell The other end of the shell 41 projects from the bottom of the cup-shaped shell 43 and is formed with a beaded edge 4l.

The elements 39 are preferably mounted in end-to-ehd relationship within the envelope 51 by securing each to a seal ring 2l. To this end, each of the rings 2| is formed with an annular fiange i9 which may be welded or otherwise fastened within the ring 2|. The elements til are provided with outstanding lugs or ngers El adapted for fastening upon the anges t in any preferred fashion, as by means of the fastening screws 53. As shown in Figures 1 and 2 of the drawing, the fingers 5| are fastened, as by welding, to the member 39 on the flange portion i5 thereof in position projecting outwardly of the shell 3. As shown in Figures 3, 4 and 5, the fingers 5l are formed on a support ring 55 which is adapted to snugly nt upon the outer wall surfaces of the member 39, the ring being secured in place in any suitable or convenient fashion as, for example, by welding it in place.

As a manufacturing convenience, the present invention provides for the mounting of the lens elements 39 in the envelope i1 after the same has been built up rather than by mounting the lens elements on the rings 2l prior to or during the fabrication of the envelope i1. To this end, the flange t9 of each lens mounting is formed with notches 51 which are spaced apart in the annular flange 49 to correspond with the spacement of the lugs or ngers 5l on the elements S9. rIhe spacement and arrangement of the lugs 5i is preferably identical in each element 35i, and the notches 51 are likewise preferably identically spaced and arranged in all of the mounting flanges 49. Each element 39, therefore, may be passed from either end of the envelope i? to its mounting ange by passing it through vall of the intervening anges, the openings 51 in the'anges allowing the lens supporting fingers 5i toV pass therethrough until the assembly reaches the flange upon which it is to be mounted. Thereupon, the lens element may be turned to odset the mounting fingers 5I thereof on thesilange 5,2, and the lens element may be secured in place by means of the fastening screws 53 Ywhich extend through openings in the .iingers `l and threadedly engage threaded sockets formed in spaced relationship in the flange 59. The screws V53 may be applied by means of a long screw driver passing from the end of the envelope through the intermediate annular ilanges 49, each lens element being successively mounted on its ksupporting ange until all have been mounted. Thereupon, theend seals carrying theanode and cathode electrodes may be applied.

The present invention .teaches the provisionof lens elements or shields within the envelope of an electron iiow device 'and contemplates the provision of novel means for mounting a series of elements whereby the elements may be mounted after the envelope has been built. The present invention further provides for the removal and replacement ci:` imperfect lenses without destroying the envelope, lens interchangeability being a valuable feature of the invention. It will be noted that the lenses in any given structure may be identical, thereby enabling the same to be made at low cost. The mounting rings also may be identical for low cost fabrication.

It is thought that the invention and its numerous attendant advantages will be fully understood from the foregoing description, and it is obvious that numerous changes may be made in the form, construction and arrangement of the several parts without departing from the spirit or scope oi the invention, or sacrificing any of its attendant advantages, the form herein disclosed being a preferred embodiment for the purpose of illustrating the invention.

The invention is hereby claimed as follows:

l. An electron flow device comprising a sealed envelope, an anode and cathode in opposed, spaced relationship in said envelope, said envelope comprising tubular wall portions enclosing the space between the anode and cathode, and electronic lens means comprising a series of lens elements supported in aligned relationship and disposed in said space between the cathode and anode to retain electrons emitted by said cathode within a predetermined flow path between the cathode and anode and to shield said wall portions against electron impingement thereon, said tubular wall portions being formed with inwardly extending supports at spaced intervals thereon, separate outwardly extending mounting means on said lens elements, and means to demountably secure said mounting means on said supports.

2. An electron ow device comprising a sealed envelope, an anode and cathode in opposed spaced relationship in said envelope, said envelope comprising tubular wall portions enclosing the space between the anode and cathode, and electronic lens means comprising a series of lens elements supported in aligned relationship and disposed in said space between the cathode and anode to retain electrons emittedby said cathode within a predetermined flow path between the cathode and anode and to shield said wall portions against electron impingement thereon, said tubular wall portions being formed with inwardly extending annular flanges spaced along the flow path between the anode and cathode, each flange being formed with notches angularly spaced therein, and means to mount the lens elements on the ilanges comprising radially extending mounting iingers on said lens elements in angular spacement thereon corresponding, with the spacement of the notches in the flanges whereby each lens element may be assembled in `the tube by passing it `from one end .of the envelope to its support flange longitudinally through the intervening other iianges, the notches in said `intervening flanges serving to pass the mounting ngers of the lens element, and means to secure the fingers on the support flange in position between ,the notches.

3. An electron flow device comprising a sealed envelope, an anode and a cathode in opposed spaced relationship in said envelope, said envelope comprising tubular wall portions enclos- 4ing the space between the anode and cathode,

an electronic lens element supported within said envelope in aligned relationship with and between said anode and cathode to retain electrons emitted by the cathode in a predetermined ow path between the cathode and anode and to shield said wall portions against electron impingement, said tubular wall portions being formed with an inwardly extending annular flange between the anode and cathode, said flange being formed with a notch, means to mount the lens element on the flange comprising a radially extending iinger on said lens element, the notch in said ange serving to pass said linger to permit the lens element to be inserted longitudinally through the flange, and means to secure the finger on the ange in position spaced from said notch.

4. An electron ow device comprising a sealed envelope, an anode and a cathode in opposed spaced relationship in said envelope, said envelope comprising tubular wall portions enclosing the space between the anode and cathode, a series of electronic lens elements supported in aligned relationship within the envelope and disposed in position between the anode and cathode to retain electrons emitted by said cathode in a predetermined now path between the cath- 0de and anode and to shield said wall portions against electron impingement, said tubular wall portions being formed with inwardly extending lens supports spaced apart in the envelope between the anode and cathode, each of said lens supports being adapted to receive and support a 1ens element, outwardly extending mounting means on each of the lens elements, each lens support and the mounting means on a lens element comprising cooperating structures, one structure comprising a projection and the other being formed with an opening through which the projection may pass when the lens element is inserted longitudinally through the envelope, and means to secure the projection on the support having the opening.

5. An electron ow device comprising a sealed envelope, an anode and a cathode in opposed spaced relationship in said envelope, said envelope comprising tubular wall portions enclosing the space between the anode and cathode, an electronic lens element supported in the envelope between and in aligned relationship with respect to the anode and cathode to retain electrons emitted by said cathode within a predetermined flow path between the cathode and anode and to shield said wall portions against electron impingement, said tubular wall portions being formed with inwardly extending support means thereon between the anode and cathode, outwardly extending mounting means on said A1ens element, the support means and the mounting means being formed to allow the lens element and the mounting means thereon to pass the inwardly extending support means whereby the lens element may be assembled in the tube by inserting it past the support means on the envelope, and means to secure the mounting means on the lens element to the support means on said envelope.

6. An electron ilow device comprising a sealed envelope, an anode and a cathode in opposed spaced relationship in said envelope, said envelope comprising tubular wall portions enclosing the space between the anode and cathode, an electronic lens element supported in the envelope between and in aligned relationship with respect to the anode and cathode to retain electrons emitted by said cathode within a predetermined iiow path between the cathode and anode and to shield said wall portions against electron impingement, said tubular wall portions being formed with an inwardly extending abutment thereon between the anode and cathode, an outwardly extending abutment on the said lens element, one of said abutments comprising a projecting iinger and the other abutment having a notch tlnough which the iinger may pass to thereby enable the lens element to be passed by the abutment on the wall portions of the envelope during assembly, and means to secure the finger on the abutment having the notch in position spaced from the notch.

HOWARD W. BRACKNEY.

JOSEPH B. GOSLING. 

